Hemodialysis is used for removing toxic wastes from the human body in cases of renal failure, and involves using an artificial kidney in conjunction with an associated machine. The patient's blood is temporarily brought outside of the body with the help of tubes and passed through at least one semipermeable membrane, which may be a group of hollow fibers, in an artificial kidney, also called a dialyzer. The semi permeable membrane separates the blood from dialysate solution. The impurities from the blood pass through the membrane and into the dialysate solutions primarily by osmotic pressures. The cleansed blood is then returned to the body. During this procedure it is also necessary to remove excess fluids from the body. This is accomplished by a process known as ultrafiltration. In this process, fluid is removed from the patient by taking the fluid off through the dialyzer via convection and discarding it. The amount of ultrafiltrate which is removed from the body is normally controlled by the pressure across the semipermeable membrane. This transmembrane pressure is the result of the differential between the blood pressure and the pressure which exists on the dialysate side of the membrane.
In an alternate procedure to hemodialysis, known as hemofiltration, convection is used to withdraw massive amounts of fluid from the body, via the dialyzer and most of that volume is replaced by ultrapure, infusate grade, fluid pumped directly into the blood stream. In this process the ultrafiltrate removal volume is the difference between the amount of fluid removed and the amount of ultrapure infusate injected. Hemofiltration is better at removing large molecular toxins than hemodialysis but is not required in most cases.
The standard dialysis treatment, using an installed apparatus in hospitals, comprises two phases, namely, (a) true dialysis, in which toxic substances and scoriae (normally small molecules) pass through the semipermeable membrane from the blood to the dialysis liquid, and (b) ultrafiltration, in which a pressure difference between the blood circuit and the circuit for the dialysis liquid, more precisely a reduced pressure in the latter circuit, causes the blood content of water to be reduced by a predetermined amount.
Dialysis procedures using standard equipment tend to be cumbersome as well as costly, besides requiring the patient to be bound to a dialysis center for long durations. Conventional systems are also less reliable because of the necessity of using a myriad of tubes comprising the fluid circuits of the purification systems, thus increasing the risks of leakage and breakage. Accordingly there is need in the art for an extracorporeal blood processing system that can be operated in hemodialysis as well as hemofiltration modes, while at the same time offering reasonable portability to the patient. Such a portable dialysis system should also be conducive to using disposable components. Further, there is also a need for novel manifolds for dialysis systems with integrated blood purification system components, such as sensors, pumps and disposables, as well as molded blood and dialysate flow paths to avoid a complicated mesh of tubing and to enhance the robustness of the system.